This invention relates to polymeric materials. Preferred embodiments relate to components which comprise first and second parts in direct contact with one another, wherein the first and second parts comprise polymeric materials having different properties. For example, the first part may be overmoulded on the second part.
In recent years, the aerospace industry has moved to greater adoption of thermoplastics composites due to the ease and speed of fabrication and the ability to combine sub-components into modular systems. One technique currently being developed is that of overmoulding composite components with standard injection moulding polymers. This enables use of relatively simple planar laminates comprising thermoplastic polymers which are overmoulded with another thermoplastic polymer to define more complex three-dimensional shapes.
Polyetheretherketone (PEEK) is a high performance, semi-crystalline thermoplastic. However, it is very difficult to overmould a second part comprising PEEK onto a first part comprising PEEK and achieve a strong bond between the first and second parts. It is an object of preferred embodiments of the present invention to address this problem.
It is also known to make components comprising first and second parts which comprise PEEK by use of epoxy resins to adhesively bond the first and second parts together. However, there are disadvantages with this approach, including the following:
(i) Any adhesive systems requires an undesirably long setting time;
(ii) The surfaces of the parts to be bonded require preparation, for example degreasing; and surface treatments, such as acid etches, laser treatment and mechanical roughening may be used;
(iii) Adhesives often involve a chemical reaction whereby they “set”. Consequently, the quality of the bond will be dependent upon, for example, temperature and humidity which will, therefore, need to be controlled.
(iv) Adhesives are usually amorphous polymers which may lead to problems in terms of chemical resistance and long term mechanical performance of the components.